Dave Naffziger's Blog

The adSense blog just announced that the ads found first in your source code get the highest paying ads. The ads found last in your source code get the lowest paying ads.

While many sites may not be affected by this knowledge (the first ad is typically the best performing anyway), you should use custom channels to carefully track each placement – make sure the ads with the highest CTR appear first in the source (you can use CSS to juggle this around).

As an example, imagine a sample page that has a small ad unit in the top right of the page, and a big unit in the center of the page. The big unit likely performs best. However, the small ad unit will get the best paying ads, leaving your best placement with lower performing ads. You want to align your best performing placements with google’s best performing ads.

This is awful for several reasons:

1. Google should be automatically doing this in the background. They are able to detect multiple ad units on a page, and they are able to determine the order with which they are called. They can also detect and calculate clicks and payouts based on the conversion of the ads that they displayed. Yeah, I know it is a extra math and extra data storage, but auto-optimizing this isn’t too hard.
2. Google is going to train publishers to use CSS to modify the source of a page (not the presentation of the page). This is a technique commonly used in ‘grey-hat’ SEO, and Google is going to force every publisher to learn it.
3. Best performing placement isn’t always clear when you consider that ad units may have different numbers of ads. An ad unit with 1 ad will usually have a lower CTR than an equivalently placed ad unit with 4 ads. That doesn’t necessarily mean that you want to highest paying ad in the second larger unit. Again, Google has all the data to solve this automatically and as always, experimentation is a must.

Oh well, good information to know and utilize. Once YPN truly supports multiple ad units (shows different ads on each ad unit), I would expect similar logic to apply there.